function faceIndex = CalcUnstructFace(mesh)

nFace = mesh.iDimensions(2);
faceIndex = cell(nFace,1);

% note here,mesh.face.face2Node is 0:nNode-1,which is node id.

iNode = 1;
for iFace = 1:nFace
    faceIndex{iFace} = ...
        mesh.face.face2Node(...
        iNode:iNode + mesh.face.nodeNumberOfEachFace(iFace)-1)+1;
    iNode = iNode + mesh.face.nodeNumberOfEachFace(iFace);
end